Embodiments relate generally to methods and apparatus to implement except conditions including, for example, implementing an except condition in data packet classification.
Except conditions can be used to exclude a portion of a range from the range. For example, an except condition for a range of Internet Protocol (“IP”) addresses can exclude one or more IP addresses from the range. Although exception conditions can be simply stated, they are generally difficult to implement succinctly in computational hardware.
Known methods of implementing an except condition rely on a negation of a match condition. Such methods can be difficult to implement in computational hardware because the negation of a match condition can yield numerous match conditions. Additionally, the numerous match conditions produced yield an increase in computational complexity and memory requirements for storing the multiple match conditions. Thus, a need exists for improved apparatus and methods of implementing except conditions in computational hardware.